Conventionally, a disaster recovery function exists as one of the data protection functions in a computer system (see PTL 1 and PTL 2, for example). A disaster recovery function is a function enabling data communication services to be continued by means of another storage system which is spared from a disaster even if a fault occurs with the storage system as a result of the disaster by copying, and shared possession of, the data stored in the storage system between a plurality of storage systems.
More specifically, supposing that a storage system which is used for normal data access is called a “primary storage system” and a storage system which is used when a fault arises in the primary storage system is called a “secondary storage system,” during normal times, the data is copied to the secondary storage system synchronously or asynchronously to the data writing to the primary storage system. Such data copying from a primary storage system to a secondary storage system is called replication.
Furthermore, if a fault occurs in the primary storage system as a result of a disaster, a secondary storage system in which a fault has not been generated switches to the primary storage system. The act of switching from the secondary storage system to the primary storage system is known as disaster recovery.